As a general rule, a V-belt transmission will provide a speed range of approximately 5.7 to 1. The maximum speed ratio between the sheaves is approximately 1.0 to 0.42. Under this condition, the output shaft will rotate at 2.39 times faster than the input shaft. This results in the top speed range starting at approximately eighteen percent of the maximum vehicle speed when the maximum engine speed is present. Another problem with most V-belt transmissions is that the belt must transmit full power during maximum vehicle speed. Also many of the systems transmit full engine power through the belt during vehicle launch. In automotive powertrains, the V-belt is the limiting power factor which prevents the V-belt from being used in larger vehicles such as trucks and large sedans. With the current technology in belt structures, the engine displacement is limited to less than three liters.
Split power systems can improve the power capacity of a transmission using a V-belt. U.S. Pat. No. 4,470,326, for example, has a split power geared neutral condition. However the upper ranges do not take advantage of this split power arrangement. The PCT publication WO 94/21941 5,643,131 also appears to disclose a split power V-belt having two speed ranges. This system employs four clutches to accomplish the two speed ranges. Also it would appear that a separate reverse gear arrangement is needed.